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With the fast growing demand for space based telecommunication capabilities in combination with application of high density electronics, the cooling requirements for future telecommunication satellites is steadily increasing, up to a point that conventional cooling technologies using (loop) heat pipes are no longer ennough to cope with in-orbit load and heat rejection variations, large number of thermal interfaces and testing constraints. To prepare for future high performance cooling requirements, the European Space Agency, ESA initiated the development of a Single-Phase Mechanically Pumped Fluid Loop (MPFL) which was one of the two heat transfer element options for the large Alphabus deployable radiator (see Figure 2).

The paper describes freezing and pressure tests required to develop a freeze-proof condenser for the Tracker Thermal Control System (TTCS). The TTCS is a mechanically pumped two-phase carbon-dioxide loop dedicated to control the temperature of the Tracker electronics. The TTCS is part of the Alpha Magnetic Spectrometer planned aboard the truss of the International Space Station (ISS). The TTCS collects the heat at two evaporators and rejects it at two radiators. In case of an accidental power-down of the AMS02 experiment, resulting in a loss of radiator heater control, the Tracker radiators and the connected TTCS-condensers may cool down as low as −120ºC, which is well below the CO2-freezing point (−56ºC@3MPa). During uncontrolled radiator heat-up and thawing of the solid CO2, liquid CO2 can be trapped in between solid parts resulting in high pressures. To withstand these high pressures, a high-pressure resistant condenser has been developed.

This paper presents selected results of four experiments into air traffic control (ATC) aspects of free flight (FF). The first two examined basic human performance implications of FF, in terms of workload and ability to monitor traffic. The third explored the potential for improved ATC displays to benefit controllers under FF traffic patterns. The fourth experiment examined methods for accommodating mixed equipage, such as during a transitional FF era in which both FF capable and FF incapable aircraft would be expected to share the same airspace. The first three experiments involved controllers operating in “open-loop” simulations, with computer-generated traffic and simulated pilot responses. In the final experiment, pilots and controllers were linked in real-time sessions.

Free Flight (FF) would permit aircraft to fly preferred routes, and self-separate, with minimal ATC intervention. The controller would be expected to intervene tactically only as necessary to ensure separation. Based on the results of earlier experiments at the NLR, an enhanced ATC display was developed that incorporated airborne-derived conflict detection and resolution information. Trials with controllers demonstrated benefits in terms of monitoring time and performance, as well as in general acceptance. Two important issues were identified for future work: (1) FF training needs and (2) controller responses to abnormal system modes.

Two-phase heat transport systems are currently considered for the thermal management of future large power spacecraft. The monitoring of the quality, being the relative vapour mass content, of the two-phase mixture at various locations in the system, is valuable - possibly indispensable - for the proper operation of such a system. This paper reviews concepts for quality monitoring. Only a few concepts turn out to be suitable for spacecraft applications. Promising concepts are based on the capacitance, sonic velocity and index of refraction. These concepts are described and quantitatively analyzed. Applicability, advantages, restrictions and some hardware aspects are discussed.